Material and methods: We retrospectively reviewed the medical records for 35 eyes of 18 patients who had undergone refractive laser surgery for the treatment of myopia and/or myopic astigmatism. We measured AL, anterior chamber depth (ACD) and central corneal thickness (CCT) using AL-Scan (Nidek CO, Gamagori, Japan). We analyzed the differences between the measurements using a two-tailed paired t test.

Results: The mean age of the patients was 26.26±6.43 years, and their mean refractive change (at the corneal plan) was -3.02±1.83 in 21 eyes of 11 patients who had undergone laser in situ keratomileusis and 14 eyes of 7 patients who had undergone photorefractive keratectomy. The AL was signifi cantly shortened after laser surgery, the mean difference in AL [?AL] was 56.86±34.45 ?m;(P<0.001). Preoperative AL values strongly correlated with postoperative values (r2=0.999). The postoperative CCT was signifi cantly thinner than the preoperative CCT (P<0.001). Mean difference between these two values (?CCT) was 55.89±27.23 ?m. There were not signifi cant differences between the mean ?AL and TAD or between ?AL and ?CCT (P>0.05). On the other hand, ?AL and TAD (r2=0.215) and ?AL and ?CCT (r2=0.184) were poorly correlated with each other, but TAD and ?CCT were strongly correlated (r2=0.814).

Conclusion: The AL-Scan device gave AL values that were inconsistent with the TAD. Since the TAD and ?CCT values were similar and were correlated with each other, this disparity might have resulted from incorrect AL measurements by the device due to a clinically subtle loss of corneal transparency in patients who had undergone myopic excimer laser surgery. Keywords : Eye length, Refractive surgery, AL-Scan